Meaning of idea of pure reason

ide'a of pure' rea'son

Pronunciation: [key]
— Kantianism. Kantianism.
  1. any of the three undemonstrable entities (a personal soul, a cosmos, and a supreme being) implicit in the fact of a subject and an object of knowledge, and in the need for some principle uniting them. Cf. ideal of pure reason.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.